This message is most often caused by leaving a floppy disk in the
floppy drive. When the machine is booted it looks the floppy drive
first. If there's a disk there, it tries to boot from it. If the
floppy isn't bootable, you get this message.

If there's no floppy in the drive, then something is drastically wrong
with the hard drive. Does the BIOS find the hard drive during bootup?
If no problems are reported there, maybe the system files in the root
directory of C: have been deleted. Boot from a bootable floppy (get
one from www.bootdisk,com if you don't have one), and type:

sys c:

Now remove the floppy and see if you can boot. If nothing works you
may have to get out your system CD and reinstall the operating system.